Field of the Invention
The invention pertains to computer security scanning methods of steganalysis, for determining whether a digital image contains a hidden payload or message.
Description of Related Art
Steganalysis is a computer security investigational method for identifying instances of steganography, namely, the hiding of a payload (hidden message) inside an electronic document or an image data file. Because of the well-known nature of various forms of text files, it is relatively difficult to embed a hidden message in a text file with any confidence that it will remain generally undetected. However, images recorded as electronic files can involve fairly large to very large data compilations, within which it is possible to embed a hidden message or payload without the image's seemingly having been altered, at least to the human eye. Steganalysis is therefore the science of finding messages hidden through steganography, typically but not necessarily in image data files.
Steganography is not new. For example, in Dr. Patrick Juola's paper entitled, “Authorship Attribution,” Foundations and Trends in Information Retrieval, Vol. 1, No. 3, 2006, pp. 233-334, steganography is discussed on page 268 as one of the ways to impart a digital watermark—authorship metadata—to an electronic document, with steganography's being described as a “well-studied and mature discipline.” However, in steganography, implanting a payload file or hidden message is the easy part—just as it is also easy to look for or to find a message or payload one already knows is present. Steganalysis is much more difficult than steganography, in that steganalysis mounts a search for a hidden message in an image data file when there is a distinct possibility that no hidden message is there at all. In a computer security context, it can be much more important to know whether an image contains a payload or not as to know what the payload is. For example, if a payload is detected, even without decrypting it, there are known ways of extinguishing payloads in image data files. A need remains for an improved, reliable security scan to assess image data files to determine the presence of absence of an unknown payload therein.